NAME__________________________________ DATE___________ PERIOD_________
CH. 4, SECTION 2: IGNEOUS ROCKS NOTES
1. The word igneous comes from a Latin word that means fire
2. Igneous rock forms when Magma (lava inside the earth) cools and hardens
3. List two factors that affect the type of igneous rock that is formed.
a. Composition (what the magma is made of)
b. Amount of time that takes to cool
ORIGINS OF IGNEOUS ROCK
4. Igneous rock begins as Magma
5. Describe the three ways that magma can form.
a. Pressure: Deep inside the earth, the pressure in the rock is released, and the
minerals can melt
b. Temperature: When minerals become hot, they can melt some, but not all minerals
c. Composition: When fluids (water) mix with rock, it lowers the melting point of the
rock enough to melt it.
6. How does the composition of the magma (meaning the minerals that make up the magma) affect the
temperature at which it solidifies?
Materials containing large amounts of liquids have lower melting points that are
different.
Materials contained in magma have different melting points, some minearls will
freeze, or become solid before other minerals do.
COMPOSITION AND TEXTURE OF IGNEOUS ROCK
7. Compare & contrast felsic and mafic igneous rocks. Include examples.
Felsic
Light Colors
Both
Rock
Mafic
Dark Colors
More dense
Less dense
Felsic and Mafic are both types of rocks. They have different materials in their
composition that makes them different densities and colors. Felistic rocks are
composed of aluminum, potassium, silicon, and sodium. Felistic rocks are light in
color, and less dense rocks like . Examples include granite and rhyolite. Mafic
rocks are composed of dense, dark materials like calcium, iron, and magnesium.
Examples of mafic rocks include gabbro and basalt.
8. The longer it takes for a rock to cool and solidify, the more time crystals have to
grow, giving the rock a(n) course grain.
9. _The more quickly an igneous rock cools and solidifies, the finer the grain.
IGNEOUS ROCK FORMATIONS
TERM
DESCRIPTION
10. pluton
Name of intrusive igneous rock based on Large size and irregularshape of the intrusive body
11. batholiths
Name of intrusive igneous rock
based on its having the largest of
intrusions
Sheet-like intrusions that cut
12. dikes
across previous rock units
Sheet-like intrusions that are
13. sills
oriented parallel to the previous
rock units.
14. Magma intrudes or pushes, into surrounding rock below the Earth’s surface to
create such formations as batholiths and sills.
15. Intrusive igneous rock usually has a(n) course grained texture
16 .Igneous rock that forms from lava, or magma that erupts onto the Earth’s surface, is called
extrusive igneous rock
17. Lava can either erupt or flow from long cracks in the Earth’s crust called fissures
18. When lava flows from fissures on the ocean floor at places where tension is causing the ocean
floor to be pulled apart, new ocean floor is formed.
19. When a large amount of lava flows out of fissures onto land, the lava can cover a large area and
form a plain called a(n) lava plateau
20. Compare and contrast intrusive and extrusive igneous rocks. Give an example of each!
Intrusive
Extrusive
Inside the crust,
Both
Earth’s surface,
Batholiths, Stocks, Sills,
Dikes,
Magma / Lava
Lava flow / eruption
spreads,
Course grain
Rock
Fine Grain
21. Write a paragraph summarizing what you have learned about igneous rocks!